Author: Stuart Cracraft
Date: 21:32:01 06/25/04
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On June 25, 2004 at 19:27:32, Andrew Williams wrote: >On June 25, 2004 at 16:15:44, Stuart Cracraft wrote: > >>So, normally in the literature I've read >>(and code I've implemented, it's been to >>do a null move search with R set to 2, >>so search(...depth-1-R). >> >>But in large searches of 8, 9, 10, 11 and >>beyond in full width searches, the reduction >>of 2 does not seem to help as much as >>larger reductions due to the much smaller >>subtrees that the null move searches has >>to search with an R of 2. >> >>My question is: what have people done >>to experiment with larger figures of R and >>verify the return value is effective >>and horrid moves aren't produced? >> >>I've used R set to ply/2 and ply-2 >>where ply is the original target depth >>of the overall iteration. The savings >>in time is substantial and the moves >>look the same or as good, the tree searched is >>drastically smaller of course, but >>I am worried about quality. >> >>Is R of 2 or 3 a holdover from the slow >>computing days in the literature and nowadays >>you are using higher settings? >> >>Assume everything else about the null move >>search is held the same (not done in endgames, >>not done in the original position, no more >>than 1 null move in a row during the search >>without an intervening normal move, etc.) >> >>Thanks ahead, >> >>Stuart > >Ernst Heinz has published interesting papers on adaptive null move pruning >(varying R with remaining depth and remaining material). I would guess that this >is pretty standard now, at least among amateurs. Omid David Tabibi has published >recently on verified null move pruning. > Hi -- I implemented the Tabibi/Netanyahu scheme from their ICCA/ICGA article today after reading your note and doing a google search for their article (found it at www.cs.biu.ac.il). Early results are promising showing verified null move with R=3 almost as good or better in most iterations than plain R=2. Thanks. Stuart
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